This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A025700 #16 Jul 06 2025 13:53:18 %S A025700 1,2,3,5,7,10,13,17,21,26,31,37,43,50,57,65,73,82,91,101,111,122,133, %T A025700 144,156,168,181,194,208,222,237,252,268,284,301,318,336,354,373,392, %U A025700 412,432,453,474,495,517,539,562,585,609,633,658,683,709,735,762,789,817,845,874 %N A025700 Index of 3^n within sequence of numbers of form 3^i * 10^j. %C A025700 First term different from A033638 is a(24) = 144 != A033638(24) = 145. %C A025700 Positions of zeros in A025685. - _R. J. Mathar_, Jul 06 2025 %o A025700 (PARI) a(n) = vecsearch(setbinop((i,j)->3^i * 10^j, [0..n], [0..logint(10^n, 3)]), 3^n); \\ _Michel Marcus_, Jun 24 2023 %Y A025700 Cf. A000244, A011557. %Y A025700 Cf. A033638. %K A025700 nonn %O A025700 0,2 %A A025700 _David W. Wilson_ %E A025700 Offset 0 from _Michel Marcus_, Jun 24 2023